In electronic packaging, one or more dies in a package can be negatively impacted by electromagnetic (EM) or radio-frequency (RF) interference. In multi-chip packages, it is difficult to completely isolate a die from being affected by the interference. It is also difficult to incorporate a digital device and an RF device, for example, in the same package because of potential interference between the devices.
A substrate is used to mechanically support and electrically connect electronic components and includes layers with both conducting and insulating materials to create conductive pathways, tracks or signal traces for the electrical components to connect to each other and/or to external connections. Conducting layers are typically made of thin copper foil while insulating layers are typically a dielectric material and are laminated together with epoxy resin.
A die used for digital applications may need to be attached to a substrate with more layers than a die used for RF applications. This may be because the die used for digital applications requires significantly more input and output (I/O) connections. On the other hand, it may be desirable that the die used for RF applications have shorter signal paths to decrease parasitic and inductance effects. Thus, the RF die may be attached to a substrate with fewer layers thereby having shorter signal paths. Conventional substrates, however, are made with the same number of layers throughout and therefore conventional packages have trouble adequately shielding or reducing EM and RF interference between adjacent dies.
Therefore, it would be desirable to develop an electronic package that can shield RF and EM interference while also meeting the layer requirements for both digital and RF die.